Direct conversion and detection of electromagnetic energy has conventionally been developed in the microwave region of the electromagnetic spectrum, where high-speed nonlinear rectifying elements, such as Schottky diodes, exist and relatively high conversion efficiencies have been attained. Wireless energy transfer to power remote devices based on radiofrequency (RF) and microwave direct rectification have been shown to be highly efficient, with greater than 84% conversion efficiency at 2.45 GHz. These direct conversion devices utilize discrete element diodes and well-developed antenna designs with impedance matching techniques to directly convert microwave radiation into a rectified direct-current.
Principles utilized in designing these devices, however, are not readily applicable for conversion of infrared (IR) radiation into electricity. With more particularity, scaling down one of the devices described above, such that elements of these devices more readily conform to IR signals has been found to be suboptimal. This is at least partially because the rectifying elements cannot be treated as lumped element devices. Moreover, carrier transport effects in semiconductor diodes are too slow to allow for direct conversion of IR radiation to electrical energy.